Chubareva L A, Petrova N A, Kachvorian E A
Zoological Institute RAS, St. Petersburg, Russia 199034.
Tsitologiia. 2003;45(4):368-76.
Karyotypes of more than 120 species of 33 genera of the Palearctic blackflies (Simuliidae) were studied on squashed acetoorcein stained preparations of salivary gland polytene chromosomes in larvae. In the course of evolution of the family, a significant complication was noticed in the morphology of centromere regions of polytene chromosomes. In plesiomorphic species, centromeres are not pronounced morphologically and the general picture does not differ from that of other bands and interbands of the polytene chromosome. In species with apomorphic characters, a distinct precentromeric heterochromatin appears, whose manifestation is responsible for morphological diversity of centromere zones in polytene chromosomes. They are represented either by conspicuous slightly thickened heterochromatic bands or by large amplified blocks of heterochromatin or puff-like structure, being considerably extended as a result of despiralization of precentromeric heterochromatin. There are species, which more commonly lack chromocentre and their chromosomes are separated. Some other species have ectopic contacts between pricentromeric heterochromatin. In some species, this heterochromatin is organized as a compact chromocentre. This has been found only in representatives of southern latitudes, most frequently in evolutionarily young species with narrow specialization.
在幼虫唾液腺多线染色体的压片醋酸地衣红染色制片上，研究了古北区蚋科33个属120多种蚋的核型。在该科的进化过程中，多线染色体着丝粒区域的形态出现了显著的复杂化。在近祖物种中，着丝粒在形态上不明显，总体情况与多线染色体的其他带和间带没有差异。在具有衍征的物种中，出现了明显的着丝粒前异染色质，其表现导致了多线染色体着丝粒区的形态多样性。它们表现为明显的略微增厚的异染色质带，或大型扩增的异染色质块或泡状结构，由于着丝粒前异染色质的解螺旋而显著延伸。有些物种通常缺乏染色中心，其染色体是分开的。其他一些物种的着丝粒前异染色质之间存在异位接触。在一些物种中，这种异染色质组织成一个紧密的染色中心。这仅在南纬地区的代表物种中发现，最常见于具有狭窄特化的进化上年轻的物种中。
